New weapons to combat oil spills

Anne Berit Bjørken

Bacteria can both consume and dissolve the heavy sticky oil known as chocolate mousse, that clogs up beaches after a shipwreck or oil-spill. This has been shown by a very comprehensive project on oil-dissolving bacteria which has recently been completed by SINTEF and NTH scientists for the FINA oil company.

The scientists have developed processes for commercial productions of such bacteria, and technology to dehydrate them with a good percentage.

"We carried out a number of trials with bacteria and oil. In all experiments, the bacteria attached themselves to the sticky oil and dissolved it. Some aspects of these processes still have to be clarified, but both we and our project sponsors would characterize the project as extremely successful," says Ivar Storrø, senior scientist at SINTEF Applied Chemistry. The basic research part of the project has been led by Professor Kjell Eimhjellen of NTH.

Eimhjellen believes that oil-dissolving bacteria, which might be produced in the form of a powder in the future, can be employed to clear up oil spills both ashore and afloat.

The bacteria eat up some of the oil and turn the remainder into a less viscous "oil-milk" of tiny oil droplets in the water. The more finely divided the oil is, the more accessible it becomes to other types of oil-eating bacteria. The great advantage of using bacteria to combat oil slicks is that we do not have to use chemicals or surfactants such as detergents.

Artificial beaches

Under natural conditions, oil and oil-containing products are broken down by a number of different mechanisms, of which naturally occurring micro-organisms are among the most important. When an oil-spill takes place, the concentration of such oil-degrading organisms increases, but it has turned out that on beaches, the rate of growth of such organisms is limited by the lack of other nutrients.

The ESCOST scientists are currently developing methods of adding nutrient components or fertilizer so that the oil bacteria can maintain a higher "rate of work" . The trials are being carried out on artificial beaches which have been built up in basins, with wave generators, simulated tides, and continuous changes of seawater. Other parameters such as temperature, salinity and light can also be varied.

The artificial beaches allow the scientists to try out the effects of different procedures under realistic conditions before field trials are carried out.

Testing oil-skimmers.

This international project is a collaborative effort involving Environment Canada, the Marine Spill Response Corporation in the USA, the US Coast Guard, the Canadian Coast Guard and SINTEF NHL. Testing, which will last for five months, is taking place in a basin in Ottawa.

"The background for our collaboration is that many tests of skimmers have already been carried out, but under different conditions, so that they are not directly comparable. There is a great deal of uncertainty regarding which skimmers should be used for different types of oil spill" says Bjørn Olaf Johannessen, a SINTEF NHL scientist.

At present, there are seven different general skimmer designs. The task of the skimmer is to take up either oil directly from the water, or after oil-booms have collected as much of the spill as possible.

"In the course of this test programme, we will test the different skimmers according to exactly the same procedures and under identical environmental conditions. This will enable us to determine which types of skimmer are most suitable for taking up different types of oil and oil/water emulsions, which in turn will put us in a better position to select the best equipment for any given action", says Johannessen.

Scientists are testing various oil-collection systems in Canada.

Standardized tests

"So far, scientists in the USA, Europe and Asia have carried out the same tests, but in different ways. This is an unnecessary waste of time. Instead of all groups carrying out the same tests, we can now use and compare each other's tests because we have a standardized method", says Johannessen. "We are currently testing five different sorbents, including bark, cellulose, synthetic cloths and sponges. The trials are being carried out in exactly the same way in all the laboratories around the world. The two objectives are to find out which materials absorb most oil, and to work out a common method.

Absorbants are used to clean up shorelines following oil spills. Laying bark, for example, on the oil makes it easier to lift the oil by means of spades and other tools. A further effect is that by covering the spilled oil, the bark prevents animals from coming into contact with it.

In the flask on the left, NTH Professor Kjell Eimhellen can monitor the oileating bacteria.

New generation of dispersants

Dispersants have traditionally been utilized to only a limited extent in oil-spill actions in Norway. This was due to their low efficiency, the high toxicity of products used 20 years ago, and the importance of the fishing industry in Norway. However, more recently developed dispersants contain only low-toxicity components that are easily broken down in nature. The active components in dispersants are surfactants or tensides that lower the surface tension at the oil-water interface and allow the oil to dissolve more easily in water in the form of tiny droplets. This is the same effect as we see in dish-washing, when we use washing-up liquids (detergents) to get fat to dissolve in the washing-up water. When dispersants are used on an oil-spill on the sea, the rate of natural dissolution of oil in water in raised, by diluting the oil more rapidly in the form of tiny droplets in the water mass.

Changes in attitudes

"All the same, there are definite limitations to the use of dispersants in combatting oil-spills. They are by no means a universal solution to the complex problems of oil-spills at sea," says Brandvik.

"The great advantage of dispersants is that they can be employed at relatively short notice on oil-spills that threaten important coastal resources. There may not be time to mobilize booms and skimmers because the oil is drifting rapidly landwards. The dispersed oil (not the dispersants themselves!) can have temporary local effects on fish and other marine organisms. This has to be balanced against the damage that the oil will do anyway to life in the sea and on the shore," says Brandvik.

As well as dispersants, the IKU scientists have developed new emulsion and shore-cleaning agents. Both categories of substance contain tensides or surfactants that reduce the surface tension at the oil-water interface. IKU Petroleum Research has done a great deal of research on alternative oil clean-up methods during the past ten years, and its project sponsors include Norwegian and foreign oil companies. The State Pollution Control Authority and NOFO have also been important supporters of IKU´s work in this field. This summer, IKU and NOFO will perform field trials with experimental oil spills and dispersants in the North Sea. These important studies will be used to verify results already obtained in the laboratory. The development of new dispersants, emulsion and shore-cleaning agents described in this article has been supported by Fina Exploration Norway.